Battery management

Abstract

A battery management system for a battery comprising at least one lithium sulphur battery cell. The battery management system comprising: a charging module operable to charge a lithium sulphur battery cell of the battery by delivering a pulsed charging current to the battery cell and to vary the duty cycle of the pulsed charging current so as to reduce the duty cycle of the pulsed charging current during charging of the battery cell.

The invention claimed is: 
     
       1. A battery comprising at least one lithium sulphur battery cell and a battery management system for the battery, the battery management system comprising:
 a charging module operable to charge a lithium sulphur battery cell of the battery by delivering a pulsed charging current to the battery cell and to vary the duty cycle of the pulsed charging current so as to reduce the duty cycle of the pulsed charging current during charging of the battery cell, 
 wherein the charging module is arranged to vary the duty cycle of the pulsed charging current such that a time-average voltage across the battery cell does not exceed a threshold voltage, wherein the threshold voltage is a voltage above which onset of a shuttle effect occurs in the lithium sulphur battery cell. 
 
     
     
       2. The battery and battery management system of  claim 1 , wherein the charging module is arranged to reduce the duty cycle of the pulsed charging current in response to increases in the state of charge of the battery cell. 
     
     
       3. The battery and battery management system of  claim 1 , wherein the charging module is arranged to charge the battery cell with a charging current having a duty cycle of substantially 100% when the state of charge of the battery cell is less than a threshold state of charge. 
     
     
       4. The battery and battery management system of  claim 3 , wherein the charging module is arranged to charge the battery cell with a pulsed charging current having a duty cycle of less than 100% when the state of charge of the battery cell is greater than the threshold state of charge. 
     
     
       5. The battery and battery management system of  claim 1 , wherein the charging module is arranged to vary the duty cycle of the pulsed charging current such that an average voltage across the battery cell is maintained substantially at a target voltage. 
     
     
       6. The battery and battery management system of  claim 5 , wherein the target voltage is the same as or less than the threshold voltage. 
     
     
       7. The battery and battery management system of  claim 1 , wherein the charging module is configured to deliver a pulsed charging current to the battery cell such that the charging current delivered during a charging pulse does not fall below a threshold charging current. 
     
     
       8. A method of charging a battery comprising at least one lithium sulphur battery cell, the method comprising:
 delivering a pulsed charging current to the lithium sulphur battery cell; and varying the duty cycle of the pulsed charging current so as to reduce the duty cycle of the pulsed charging current during charging of the battery cell, 
 wherein the duty cycle of the pulsed charging current is varied such that a time-average voltage across the battery cell does not exceed a threshold voltage, wherein the threshold voltage is a voltage above which onset of a shuttle effect occurs in the lithium sulphur battery cell. 
 
     
     
       9. The method of  claim 8 , wherein the duty cycle of the pulsed charging current is decreased in response to increases in the state of charge of the battery cell. 
     
     
       10. The method of  claim 8 , comprising charging the battery cell with a charging current having a duty cycle of substantially 100% when the state of charge of the battery cell is less than a threshold state of charge. 
     
     
       11. The method of  claim 10 , comprising charging the battery cell with a pulsed charging current having a duty cycle of less than 100% when the state of charge of the battery cell is greater than the threshold state of charge. 
     
     
       12. The method of  claim 8 , wherein the duty cycle of the pulsed charging current is varied such that an average voltage across the battery cell is maintained substantially at a target voltage. 
     
     
       13. The method of  claim 12 , wherein the target voltage is the same as or less than the threshold voltage. 
     
     
       14. The method of  claim 8 , wherein comprising delivering the pulsed charging current to the battery cell such that the charging current delivered during a charging pulse does not fall below a threshold charging current.